Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a nacelle fixed atop a tower, a generator and a gearbox housed with the nacelle, and a rotor configured with the nacelle having a rotatable hub with one or more rotor blades. The rotor blades capture kinetic energy of wind using known airfoil principles. The rotor blades transmit the kinetic energy in the form of rotational energy so as to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
At least some known nacelles include a yaw system for controlling a perspective of the rotor relative to a direction of wind. Such yaw systems generally include a yaw bearing, a plurality of yaw drives that operate to rotate the yaw bearing, a controller, one or more batteries, a grid anemometer, etc. Further, the wind turbine also includes sensors for sensing a direction of the wind. Thus, the controller is configured to adjust the yaw of the wind turbine via the yaw system based on the sensed wind direction.
There are instances, however, where the controller may be offline, such as for example, adverse grid or weather events (e.g. typhoons, hurricanes, etc.) as well as regular maintenance. If the controller is offline, there is no way to operate the yaw system. Without the yaw system, the wind turbine may be subjected to increased loads (e.g., asymmetric loads) that result from yaw misalignment which may contribute to significant fatigue cycles on the wind turbine components. As the wind turbine components become worn, the wind turbine becomes less effective. In addition, the wear on the component may impact the machine life adversely.
To minimize the negative effects mentioned herein, it would be advantageous for the wind turbine to include a protection logic that requires the highest availability of the yaw system to steer the nacelle to align with the wind direction or out of the wind direction in case very high wind speeds. Thus, the present disclosure is directed to an improved yaw control system and method for operating same that provides individual failsafe parallel redundant controls so as to isolate the system from failure due to malfunction or failure of any one component.